Area researchers demonstrate installation of gypsum curtain
By SEAN CLOUGHERTY
CRISFIELD, Md. — Researchers collaborating from several institutions are hoping a new research project will mean closing the curtains on phosphorus in the ground water moving into drainage ditches and Chesapeake Bay tributaries.
At a field day last week on Steve Cullen’s Somerset County farm, researchers from the University of Maryland Eastern Shore, USDA’s Agricultural Research Service and the University of Maryland College Park demonstrated the installation of a “gypsum curtain” along field drainage ditches to test their effectiveness in removing phosphorus moving in the groundwater.
To install a gypsum curtain, a 12- inch trench is dug on both sides of a drainage ditch, each is filled with gypsum then covered with topsoil and returned to its original contour so the area can be farmed again.
As ground water in the soil profile moves toward the ditch and through the curtain, soluble phosphors in the water reacts with the gypsum’s high concentration of calcium to form insoluble calcium phosphate which stays in the gypsum as the water moves into the ditch.
Research-scale gypsum curtains were installed two years ago at UMES and data from them has shown a phosphorus removal rate of about 90 percent.
Now with a $1 million Conservation Innovation Grant from USDA’s Natural Resources Conservation Service and a $1 million match from Excelon Corporation-Constellation Energy, which is providing the gypsum for the project, the researchers want to see how the curtains will do in a field scale setting.
“It looked promising enough that it was worth going to this scale,” said Ray Bryant, a USDA soil scientist and one of the lead investigators on the project. “The only way to know (if it works) for sure is to try it and that’s why we’re here.”
The researchers are testing the water quality in the curtained ditch as well as monitoring the ground water on both sides of the gypsum curtains.
Other goals of the project include measuring the curtain’s effectiveness across different soil types, identify potential adverse environmental impacts, get input from producers on the practice in the context of whole farm operations, develop a cost structure for installation and maintenance and work with NRCS to develop standards for the practice.
Jon Hall, Maryland NRCS state conservationist attended the field day and said the grant program that funded this project is intended for developing and adopting new conservation practices.
If the project’s data continues to show promise in removing phosphorus, Hall said that the NRCS would develop standards for installation, adoption and technical assistance and bring it before the agency’s state technical committee for review as a best management practice which could then come with cost share opportunities.
Once enough data is available, that process could take about two years, Hall said.
“Most of it depends on the research,” Hall said. “I’m pretty exited about seeing it today. It has a lot of potential for innovation.”
Two fields will have curtains installed this year and two more next year, according to Bryant.
Another part of the project includes studying the benefits of field application of gypsum for increased infiltration and drainage.
Better soil drainage would move more water through the curtain eventually, Bryant said, rather than leave the field as surface runoff.
The Lower Shore is an ideal area for using the curtains, Bryant said, where high levels of “legacy phosphorus” from poultry litter applications remain in the soil and the dominate pathway of phosphorus movement is through the ground water rather than surface runoff.
The gypsum in this case is a byproduct of flue gas desulfurization in coal-fired power plants.
While wallboard for construction purposes is one of the main uses for the gypsum, power plants generally produce a great deal more than wallboard makers need and are interested in other uses.
“You’re taking a product that was going to a landfill and using it to clean up the Chesapeake Bay,” Bryant said.
Bryant estimates the effective lifespan for a curtain at about 10 years though that is also something he hopes the research will be able to further define.